Many processes for the catalytic production of glycols from lactones have been developed. Among the glycols in high demand are those having four or more carbon atoms such as 1,6-hexanediol and especially, 1,4-butanediol.
Glycols such as 1,4-butanediol and 1,6-hexanediol are useful as monomers in a number of polymers including, thermoplastics such as the polyester thermoplastics and polyether thermoplastics. Examples of such thermoplastics include poly(1,4-butylene terephthalate) resin block copolymers containing blocks of poly(butyl ether) and aliphatic polyesters such as poly(hexylene adipate).
Particularly, 1,4-butanediol may be produced by a number of processes, among which is the production in a single hydrogenation step from a diester of maleic acid or in a two step process converting maleic anhydride first to gamma-butyrolactone and subsequently in a second reaction step to 1,4-butanediol. Several references have dealt with the conversion of gamma-butyrolactone to 1,4-butanediol, the majority of which recommend the liquid phase for carrying out the reaction. However, it is known to conduct the reaction in the vapor phase as well.
WO No. 82/03854, Bradley, et al., discloses the hydrogenolysis of gamma-butyrolactone in the vapor phase over a copper oxide and zinc oxide catalyst. Reactor productivity in this process is generally low.
British Pat. No. 1,230,276 discloses the hydrogenation of gamma-butyrolactone using a copper oxide-chromium oxide catalyst. The hydrogenation is carried out in the liquid phase. Batch reactions are exemplified having very high total reactor pressures. Reactant and product partial pressures in the reactors are well above the respective dew points.
British Pat. No. 1,314,126 and U.S. Pat. No. 4,652,685 discloses the hydrogenation of gamma-butyrolactone in the liquid phase over a nickel-cobalt-thorium oxide catalyst. Batch reactions are exemplified having high total pressures and component partial pressures well above respective component dew points. Like the process above, this catalytic reaction is time consuming and expensive to operate.
British Pat. No. 1,344,557 and U.S. Pat. No. 4,652,685 discloses the hydrogention of gamma-butyrolactone in the liquid phase over a copper oxide-chromium oxide catalyst. A vapor phase or vapor containing mixed phase is indicated as suitable in some instances. A continuous flow tubular reactor is exemplified using high total reactor pressures. The selectivity of these processes is not entirely satisfactory due in part to the moderate activity of the catalyst.
British Pat. No 1,512,751 discloses the hydrogenation of gamma-butyrolactone to 1,4-butanediol in the liquid phase over a copper oxide-chromium oxide catalyst. Batch reactions are exemplified with high total reactor pressures and, where determinable, reactant and product partial pressures well above the respective dew points. However the process suffers the same objections pointed out above.
U.S Pat. No 4,301,077 discloses the hydrogenation to 1,4-butanediol of gamma-butyrolactone over a Ru-Ni-Co-Zn catalyst. As taught, the reaction may be conducted in the liquid or gas phase or in a mixed liquid-gas phase. Exemplified are continuous flow liquid phase reactions at high total reactor pressures and relatively low reactor productivities.
U.S. Pat. No. 4,048,196 discloses the production of 1,4-butanediol by the liquid phase hydrogenation of gamma-butyrolactone over a copper oxide-zinc oxide catalyst. Exemplified is a continuous flow tubular reactor operating at high total reactor pressures and high reactant and product partial pressures.
While the process of the above references are convenient to produce small quantities of 1,4-butanediol, on scale-up, it is discovered that generally low reactor productivities necessitate large reactors to produce commercial quantities. Such large reactors are impractical using the high pressures of the prior art references.
Accordingly, it is an object of the present invention to overcome the above deficiencies and to produce glycols from lactones, and in particular, 1,4-butanediol from gamma-butyrolactone in high yield and selectivity.
It is another object of the present invention to markedly increase reactor productivity in the hydrogenation of lactones to diols.
It is another object of the present invention to provide a highly active catalyst for improved diol selectivity which catalyst can be prepared by an economical and commercially feasible process.
These and other objects of the invention will become apparent from the following description and disclosure.